1. Field of the Invention
The present invention generally relates to an image processing technique and, more particularly, to a technique which is used for accurately recognizing characters filled in an area defined by ruled lines by deleting the ruled lines existing adjacent to the characters in an image of a ruled form.
2. Description of the Related Art
Japanese Laid-Open Patent Application No. 7-57047 discloses a method for deleting a ruled line in an image obtained from a document containing characters and ruled lines. In this technique, an entire image of the document is scanned so as to extract lines extending in a predetermined direction. Each of the extracted lines is classified into either a ruled line group or a character group in accordance with a ratio of a vertical length and a horizontal length of a circumscribed rectangle which encircles a group of adjacent lines. In order to obtain an image corresponding to only characters, a part of the ruled line group which does not overlap the character group is deleted so that the lines corresponding to a character are not deleted.
In the above-mentioned conventional technique, an entire image must be processed and, thus, there is a problem in that it takes a long time to complete a ruled line deleting process. Additionally, in the conventional technique, since a group of lines is classified into ruled lines or characters, if a threshold level is set so that a short ruled line is positively determined to be a ruled line, a stroke of a character may be determined to be a ruled line. Contrary, if the threshold level is set to decrease probability of occurrence of such an erroneous recognition, a short ruled line cannot be deleted since it is determined to be a part of a character. Accordingly, there is a problem in that it is difficult to simultaneously achieve both accurate deletion of ruled lines and accurate prevention of erroneous deletion of characters.